Solve for $x$ and $y$ using substitution. ${4x-y = 1}$ ${y = x-7}$
Solution: Since $y$ has already been solved for, substitute $x-7$ for $y$ in the first equation. ${4x - }{(x-7)}{= 1}$ Simplify and solve for $x$ $4x-x + 7 = 1$ $3x+7 = 1$ $3x+7{-7} = 1{-7}$ $3x = -6$ $\dfrac{3x}{{3}} = \dfrac{-6}{{3}}$ ${x = -2}$ Now that you know ${x = -2}$ , plug it back into $\thinspace {y = x-7}\thinspace$ to find $y$ ${y = }{(-2)}{ - 7}$ $y = -9$ You can also plug ${x = -2}$ into $\thinspace {4x-y = 1}\thinspace$ and get the same answer for $y$ : ${4}{(-2)}{ - y = 1}$ ${y = -9}$